bionx bike systems

A friend of mine is planning on setting up a bike or buying a bike from these guys.

We need to modify the system so that a battery is always being charged, when under generation and one battery is used under power. So there is a backup. And or boost when needed.. He's thinking of taking his paraplegic friend along for the ride.. And i'm thinking this system may be to weak for it.

But he is more interested in generating electricity that can then be used for other things.. like to power appliances in home..

What i'm looking for to help him is some schematics.. where and how could we hook up this other batter, and the switch needed to turn it off and on..

And then how to wire it on another switch for boost. without friing the controller for it..